The invention relates to apparatus for locking doors. While particularly suited for locking of sliding glass doors, it will be understood that it does also have application to other hinged doors. The prior art includes locking apparatus which uses a single lock cylinder on one side of the door and a handle on the other side of the door which each operate the locking member. Such locks permit the homeowner to exit through the doorway of the sliding door and then lock the door using a key which cooperates with a locking cylinder on the other side of the door.
With the prior art apparatus a burglar may enter the building equipped with such a door lock and then may simply unlock the sliding door by turning the handle on the interior side thereof and pass out of the building with bulky objects such as television sets, stereos and the like. This problem is most acute with sliding doors which typically open onto a patio, not only because of the larger glass door permits the passage of large objects, but also because the door is typically located on the rear of the building where the exit by unauthorized persons will not be observed. The mode of operation to remove bulky objects is used commonly enough to justify apparatus which will prevent a burglar from exiting from a sliding door after he has once gained admittance to the building through some other entrance way.
Accordingly it is an object of the invention to provide apparatus which will more positively prevent exit through the doorway of a sliding door by unauthorized persons.
Still another object of the invention is to provide apparatus which is relatively strong and relatively invulnerable to being broken as by a hammer blow.
It is still another object of the invention to provide apparatus which will also function as a handle.
Still another object of the invention is to provide such a handle which will be contoured in a manner which will facilitate the operation of the door even when the user's hands are full.